This proposal is based on studies of the methylerythritol-4-phosphate (MEP) pathway that synthesizes the universal precursors of isoprenoid compounds, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), in which we have identified potential drug targets in Mycobacterium tuberculosis and other bacterial pathogens. These targets also exist in Plasmodium and Toxoplasma species. The enzymes involved in the MEP pathway in pathogenic bacteria have recently generated a great deal of attention as a source of targets for novel antimicrobials; all enzymes in the MEP pathway are thought to be potential targets for novel drugs as the MEP pathway has been demonstrated to be essential in both Gram-positive and Gram-negative bacteria and human cells do not contain orthologs. In addition, a natural antibiotic, fosmidomycin, which inhibits the second enzyme in the pathway (IspC) also inhibits the growth of Gram-negative bacteria and we have shown that inhibitors of the first enzyme in the MEP pathway (Dxs) also inhibits the growth of M. tuberculosis. However, few laboratories have been able to pursue this topic in detail due to a lack of substrates and appropriate HTS amenable assays. Our previous work in this area was aimed at characterizing MEP pathway enzymes from bacterial pathogens and developing efficient syntheses for the substrates; our present goal is to identify and develop inhibitors of previously characterized enzymes to provide potential leads for development of novel antimicrobial compounds.